Ventilated radio-shielded spark plug



June 6, 1944. M. F. PETERS ETAL VENTILATED RADIO-SHIELDED SPARK PLUG Filed April 6, 1942 Patented June 6, 1944 UNITED STATES PATENT- OFFICE VENTILATED RAgiQj-HIELDED SPARK Melville F. Peters, Beltsville, Md., and David Ingalls, Westileld, N. J assignors to Titeilex, Inc.,

a corporation of New'Jersey Application April 6, 1942, Serial No. 437,910

' 31 Claims. (01. 123-169) This invention relates to the ventilation of chambers within the radio-shielding of electrical connections, particularly the connections between an ignition cable with the electrode of the spark plug of an internal combustion engine which are located in a chamber in the radio-shielding for the spark plug. The invention may, however, have other applications.

As is well known, a spark plug is usually shielded by a tubular, metal structure electrically connected with the portion of the spark plug which is grounded on the engine block, such tubular, metal structure surrounding the upper portion of the spark plug so that the bare central electrode and the bared end of the ignition conductor are placed in electrical connection atabout midway of the length of the tubular, metal shielding.

This tubular shielding is lined with a cylinder of insulation so that any flash-over from the bare electrical conducting parts as referred to, to the metal of the shielding must be beyond the end of the insulating cylinder and the path of any flash-over is thereby greatly increased and the danger of its occurrence is lessened. It has been found, however, that even under these circumstances there is sometimes difficulty in flash-over 'between the parts as indicated which may be due to break-down of the resistance of the air gap because of contamination of the air by nitric- .oxide or other vapors found in the chamber and which probably seep thereinto from the engine cylinder, or ionization of the air or from other causes. l

The deleterious conditions referred to may be relieved against by proper ventilation of the chamber within the radio-shield, and it is the main object of the present invention to provide suitable ventilation whereby the disadvantages .as indicated are avoided, and the invention is also applicable to radio-shielded electrical connections otHer than those-between an ignition conductor and-a spark plug. To this end a suitable venting means is provided which shall not interfere with the proper construction and functioning of the parts, particularly with regard to provision for proper insulation of the parts and prevention of flash-over.

Inasmuch as the insulating lining of the cham- It is a further object of the invention to clear out all noxious gases from the electrode chamber especially atthe bottom thereof, where such gases are sure to be found, if anywhere, as it is at this'point that the presence of gases in the chamber, is initiated. To this end the venting takes place aboutthe bottom end of the insulating lining which is the end nearest the engine.

With the vent open, the natural convection or circulation of the air from the interior of theelectrode chamber to the external atmosphere, especially when the plug and connected metal parts are at a high temperature due to high horse power' output of the engine, may prove reasonably s'uflicient. It, is a further object of. the invention, however, to render the ventilation more reliable, better; regulated and efficient, which is accomplished by applying pressure to the gaseous contents of the chamber.

While it is desirable that the gases from the electrode chamber should be vented outwardly to the atmosphere as stated, it is usually not desirable that the exterior atmosphere should flow into the chamber, and its connected clearances, because of the danger of carrying thereinto'deleterious materials, such as moisture or other undesirable vapors or gases. It is, therefore, a further object of the invention to provide means which shall prevent the inflow of outside atmosphere into the chamber.

The tendency of inflow of outside atmosphere into the chamber will usually be when the engine is not in operation, when the spark-plugs are cool and any pressure means employedis not in operation and, therefore, it is a further object of the invention to provide means for controlling the vent in accordance with operating conditions of the engine.

One of the operating conditions of the engine is the heating of the spark plug, and it is a furher within the shielding; cannot be punctured ther object of the invention to make use of the temperature fluctuations of the spark plug or its connected metal parts to control the venting.

Other and ancillary objects of the invention will appear hereinafter.

In the accompanying drawing which illustrates the invention; I

Fig. 1 is a side elevation, partly broken'away and partly in, section of a ventilated radio-shielded spark plug, connections therefor and 'structures appurtenant thereto, according to the invention;

Fig. 2 is a section, on an enlarged scale, on th line 2-2 of Fig. 1;

Fig. 3 isa diagrammatic view of a radio-shielded ignition system for an internal combustion engine with fluid pressure applied thereto, em-

' grammatic representation of a common form of a radio-shielded ignition system for internal combustion engines, especially of a radial cylinder type such as commonly employed upon aeroplanes. In this Fig. 3 the ignition conductorsextend from a radio-shielded magneto I through a radio-shielded conduit 2 extending between the shield of the magneto and a radio-shielding manifold 3 secured to the engine. From the manifold extend individual radio-shielding conduits 4 each containing an ignition conductor leading to one of the radio-shielded spark plugs 5 of the engine. Each conductor, therefore extends from the magneto through the conduit 2 and the manifold 3 and an individual conduit 4 to its spark plug 5. I r

In the diagram of Fig. 3, a dual ignition system is shown having, in addition to the set of spark plugs 5 connected with the magneto I, another set of plugs 5 connected with another magneto. The conduit fromthe last magneto is connected with the manifold at 2, the conduit being broken away and the second magneto omitted as not being necessary to an understanding of ,the present invention.

Connected with the conduit 2 is a pipe-6' leading to a source of compressed air or other fluid under'pressure which it is desired to maintain in the conductor conduits under pressure. Different fluids may be employed if desired but usually, air, properly conditioned would be-employed for that purpose. .There is clearance in the conduit 2, manifold 3 and spark plug lead conduits 4 so that air supplied under pressure through the pipe 6' to the conduit 2 may pass through the conduit to the manifold and the spark plug leads and to any chambers in or related to the spark plug, connected therewith.

' With regard to each of the spark plugs 5,- the metal radio-shielding conduit 4 is firmly secured acts as a radio shield'for the enclosed extremities of the ignition cable and the spark plug. The tubular member l4, it will be observed, is in good conducting relation both as to heat and electricity with the spark plug nut l2 and through it with the shell 1. The end of the metal elbow 6 is secured in firm electrical and mechanical relation to the member l4 means of a ring nut l5 screw-threaded to the member l4 and having an inturned flange l6 overlapping the flange H at the end of and integral with the elbow 6, the flange I] being in good electrical contact with the end of the member I4 through the nut l5, a rubber gasket l5 being compressed between the flange l1 and the end of the tubular member l4 and forming a fluid-tight joint at that location.

The ignition cable comprises the copper conductor I8 'upon which is carried the insulation IS in the well-known manner of insulated electric conductors. This conductor passes from the conduit 4 through the elbow 6 into the interior of the tubular member l4. The end 20 of the conductor I8 is soldered within the socket portion 2| of a metal terminal connector which also-comprises the globular clip 22, this globular clip being split longitudinally as shown to form spring fingers which grip about and secure the nection with the metal globular head-23 which is screw-threaded upon the central spark plug electrode Ill.

both mechanically and electrically to a tubular 1 metal radio-shielding elbow 6. The spark plug comprises a threaded metal shell 'I which is screw-threaded into the engine block and hence is grounded. Upon the lower end of the shell is the grounded outer sparking point 8, while the central sparking point 9 is the lower end of the central electrode l0. secured to and supported by the surrounding porcelain body having the upper tapered portion II, the porcelain body,v

with the central electrode, being secured in the shell by a nut II. The construction of the spark plug as described thus far is well understood in the art.

Secured to and integral with the nut I2 is a metal socket piece l3 screw-threaded upon its' interior and into which is screw-threaded the lower end of a metal, tubular member l4 which The inner bore of the tubular member l4 has a cylindrical insulating lining 24 which may be of mica or other suitable insulating material and which extends substantially throughout the length of such bore. A metal ring 26' of U- shaped cross section is pinched on to, the upper end of the mica cylinder 24 to reenforce the structure and flrmly secure theparts together.

Exposed metal parts connecting together the ignition cable conductor and the central electrode of the spark plug, are within the chamber 25 surrounded by the shielding member l4 and the insulated sleeve 24 and approximately midway between the ends of,-whereby a long gap is provided from the bare metal connecting parts referred to, to the other metal parts of the structure and danger of flash-over from the bare electrode parts to the metal of the enclosing structure is greatly reduced. if not entirely obviated.

It willbe seen that the electrode chamber 25, that is the chamber containing the bare metal electrode and connection parts is in communication with the clearance about the ignition conductor in the elbow 6 and thence with the clearance about the cable in the conduit and is, therefore in communication with the source of air pressure as before referred to. The chamber 25 is thus subjected'to' such air pressure.

Small openings or notches 26- formed in th bottom of the insulating sleeve 24 establishes connection at the bottom of the chamber 25 with a slight clearance 21 between the sleeve 24 and the tubular member H, which clearance communicates, with the atmosphere through a vent 21 and outwardly through the opening 28 to the atmosphere when the channel 28 is open. Such seeping of the air through the entire length of the electrode containing chamber will efiectively clear out all noxious fumes or gases which may be in the chamber, such gases being particularly liable to be in the extreme bottom of the chamber. The flow of gas from the electrode chamber 25 outwardly through the vent would ordinarily not be great in volume but a slight seepage would be suflicient .to adequately clear the electrode chamber of the noxious gases referred to. v Under such circumstances it may be that the usual clearance between the insulating lining sleeve and the wall of the tubular sleeve will be sufllcient without the necessity of providing any special clearance, and also the lower edge of the said insulating sleeve might be suiiiciently rough to provide the necessary seepage passages without specially formed notches therein or other specially formed channels for the passage of the fluid from the inside to the outside of the insulating sleeve.

It not being desirable to have atmospheric air, either damp or otherwise unsuitable, enter through the vent to the electrode chamber and connected clearances throughout the shielding, the valve 29 is provided which, when against its seat in the end of the vent passage28, closes the vent, and when the valve is moved away from its seat, the vent is accordingly opened. This valve 29 is mounted upon a thermostatic bi-metallic ring 30 which surrounds the tubular member 14, such ring being severed at 34, bi-metallic thermostat structures of this character being well known. This ring is mounted in slots or channels 3| in the exterior of the tubular member i4 and the side of the ring, diametrically opposite the valv'e 29, is secured to the member [4 by a screw 32. The ring is therefore in intimate heat transferring contact with the metal member l4 and through it with the spark plug.

When the engine is in operation and consequently the spark plug becomes hot, the ring 30 will be accordingly affected and the valve 29 will be lifted from its seat thereby opening the vent accordingly, the greater the heat the greater expansive operation of the ring and greater opening of the vent so that there will be a greater flow of air for increased horse power output of the engine. During engine operation the conditioned air under pressure will be applied to the chamber 21 and the flow or seepage from the. electrode chamber 25 to the atmosphere will take place with advantageous results as noted. When, however, the engine is not in operation, the air pressure is not applied to the interior of the shielding conduits, also the parts will become cool, and therefore undesirably conditioned air might seep inwardly from the atmosphere to the electrode chamber it means were not provided to prevent it. This undesirable condition is prevented because of the action of the ring 39 when the spark plug and connected parts cool down, this action of the ring causing the seating of the valve 29 and the closing of the vent.

Referring to Fig. 6, there is shown a modified form of thermostatic ring for controlling the vent for the electrode chamber as referred to in connection with the apparatus of Fig. 1. According to Fig. 6 the thermostatic control ring 30' which takes the place of the ring 39 and valve 29 of Fig. 1, encircles the tubular member l4 and controls the vent 28, is homogeneous and made of an alloy having a high coefiicient of expansion in relation to the material of member it under increase in temperature, such alloys being well known. This ring 39' is of trapezoidal cross section, tapering inwardly, and located in a groove 3 l having a cross section of corresponding shape into which the ring is drawn to close the vent 28 at ordinary temperatures, the ring moving outwardly to open the vent upon heating of the parts during operation. The ring is severed like the ring 39 and secured to the tubular member H by a screw at the opposite side from the vent 28 as inthe case of the ring 39.

Fig. 5 is the same as Fig. 6 except that the thermostatic ring 30" is of rectangular cross section and the groove in which it lies is correspondingly shaped so that on contraction the inner face of the ring will close the vent.

In Fig. 4 the ring 30 and valve 29 of Fig. l are in Fig. 1 replaced by a spiral. coiled, flat band, steel spring 30", similar to a watch spring, having one end secured at 33 to the tubular member l4 and lying flat against the exterior wall of the tubular member I thereby closing the end of the vent 28 when the spring is in contracted condition under ordinary temperatures. On rise in temperature the spring will expand, forming a clearance between it and the outer surface of the member H thereby opening the vent.

While the invention has been illustrated inwhat are considered its best applications it may have other embodiments within the scope ofv the appended claims without departing from its spirit and is not, therefore, limited to the structures shown in the drawing.

'What is claimed is:

1. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a, source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a lateral vent to the atmosphere from said chamber to the exterior of said shielding structure and an intake opening for fluid under pressure, and means for supplying fluid under pressure to said chamber through said intake opening.

2. The combination with a spark plug, comprising a shell adapted to be fixed to an engine block and an electrode adapted to be connected to a source of current supply, of a radio-shielding, hollow structure in electrical connection with said shell and surrounding an electrode chamber containing an end of said electrode adapted to be connected to said source of current supply,

said hollow structure having a lateral vent to the atmosphere from said electrode chamber to the exterior of said shielding structure and an intake opening for fluid under pressure, and a means for supplying fluid under pressure to said chamber through said intake opening.

3. The combination with a spark plug having a shell adapted to be aflixed to an engine block and an electrode to be connected to a source of current supply, of a, radio-shielding, hollow structure in electrical connection with said shell and surrounding an electrode chamber containing an end of said electrode, a radio-shielding conduit connected with said hollow structure, a conductor within said conduit and extendin within said hollow structure and being electrically connected with said electrode end, said hollow structure having a lateral vent to the atmosphere from said chamber to the exterior of said hollow structure and anintake opening for fluid under pressure,

and means for supplying fluid under pressure to said electrode chamber through said intake opening.

4. The combination with a spark plug having a shell adapted to be aflixed to an engine block and an electrode to be connected to a source of current supp y, of a radio-shielding, hollow structure in electrical connection with said shell and surrounding an electrode chamber containing an end of said electrode, a radio-shielding conduit connected with said hollow structure, a conductor within said conduit and extending within said hollow structure and being electrically connected 'with said electrode end, said hollow structure having a lateral vent to the atmosphere from said chamber to the exterior of said hollow structure and an intake opening for fluid pressure, and means for supplying fluid under pressure to said electrode chamber through said intake opening, said vent connecting with said electrode chamber adjacent the bottom thereof.

5. The combination with a spark plug having a shell adapted to be aflixed to an engine block and an electrode to be connected to a source of current supply, of a radio-shielding, hollow structure in electrical connection with said shell and surrounding an electrode chamber containing an end of said electrode, a radio-shielding conduit hollow structure and being electrically connected with said electrode end, said hollow structure having a vent to the atmosphere from said chamher to the exterior of said hollow structure and an intake opening for fluid pressure, a hollow member inside said hollow structure and surroundingsaid chamber, said vent connecting with said chamber through passages between saidmember and said structure and about one end of said member and means for supplying fluid under pressure to said electrode chamber through said intake opening.

9. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to ,be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular. shielding structure having a vent to the atmosphere from said chamber to the exterior of said shielding structure, a cylinderof insulation inside said structure and surrounding said chamber, said vent communicating with said chamber through passages 'between said cylinder and structure and an intake opening for fluid pressure, and about one end of said cylinder and means for supplying fluid under pressure to .said electrode chamber through said intake nected to a source of current-supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure, a cylinder of insulation inside said structure and surrounding said chamber, said vent communicating with said chamber through passages between said cylinder and structure and about one end of said cylinder. 7. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure, a cylinder of insulation inside said structure and surrounding said chamber, said vent communicating with said chamber through passages between said cylinder and structure and about the bottom end of said cylinder.

8. Thecombination with a spark plug having a shell adapted to be aflixed to an engine block and an electrode to be connectedto a source of current supply, of a radio-shielding, hollow structure in electrical connection with said shell and surrounding an electrode chamber containing an end of said electrode, a radio-shielding conduit" connected with said hollow structure, a conduc-.

opening.

10. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, ofa

tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent to the atmosphere from said chamber to the exterior of said shielding structure and an intake opening for fluid pressure, a cylinder of insulation inside said structure and surrounding said chamber, said vent communicating with said chamber through passages between said cylinder and structure and about the bottom end of said cylinder and means for supplying fluid under pressure to said electrode chamber through said intake opening.

11. The combination with a spark plug having a central electrode, one end of which is a sparking point and-the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to theexterior of said shielding structure and means for controlling said vent.

12. The combination with a spark plug having a central electrode, one end of which is a sparkingpoint and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last men-. tioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure and thermostatic means for controlling said vent.

tor within said conduit and extending within said 75 13. The combination with a spark plug havmg a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure and means for controlling said vent according to operating conditions.

14. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to'the exterior of said shielding structure and bi-metallic, thermostatic means for controlling said vent.

15. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of. current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure havinga vent from said chamber to the exterior of said shielding structure and means having a high-coefiicient of expansion for controlling said vent.

16. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end 01. said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure and means controlling said vent comprising a spiral coil of heat-expansible material.

17. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radioshielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure and means for controlling said vent, said means comprising a member encircling said tubular structure.

18. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure and means for controlling said vent, said means comprising a thermally-operated member surrounding said tubular structure.

19. The combination with a spark plug having a central electrode, one end of which is a sparking point and the other end is adapted to be connected to a source of current supply, of a tubular, radio-shielding structure having in it an electrode chamber containing the last mentioned end of said electrode, said tubular, shielding structure having a vent from said chamber to the exterior of said shielding structure and means for controlling said vent, said means comprising a thermally-operated member surrounding said tubular structure and lying in a groove thereof.

20. The combination with an ignition conductor for aninternal combustion engine, of a radio-shielding means for said ignition conductor having a vent from the interior to the exterior of said radio-shielding means and means for controlling said vent.

21. The combination with an ignition conductor for an internal combustion engine, of a radio-shielding means for said ignition conductor having a vent from the interior to the exterior of said radio-shielding means and means for controlling said vent according to operating conditions of said engine.

22. The combination with an ignition conductor for an internal combustion engine, of a radio-shielding means for said ignition conductor having a vent from the interior to the exterior of said radio-shielding meansand thermostatic means for controlling said vent.

23. The combination with a spark plug for an internal combustion engine, of a tubular, radioshielding casing grounded on said engine through said spark plug, said radio-shielding structure surrounding a chamber and said spark plug having an electrode with an end projecting into said chamber, a radio-shielding conduit mechanically and electrically connected to said tubular structure, anignition conductor in said conduit and extending into said chamber to establish electrical connection with said electrode, there being spaces in said conduit in communication with said chamber and a vent from said chamber to the exterior oi. said radio-shielding, tubular structure and means for controlling said vent.

24. The combination with a spark plug for an internal combustion engine, of a tubular, radioshielding casing grounded on said engine through said spark plug, said radio shielding structure surrounding a chamber and said spark plug having an electrode with an end projecting into said chamber, a radio-shielding conduit mechanically and electrically connected to said tubular structure, an ignition conductor in said conduit and extending into said chamber to establish electrical connection with said electrode, there being spaces in said conduit in communication with said chamber and a vent from said chamber to the exterior of said radio-shielding, tubular structure and thermostatic means for controlling said vent. I

25. The combination with a spark plug for an internal combustion engine, of a tubular, radioshielding casing grounded on said engine through said spark plug, said radio-shielding structure surrounding a chamber and said spark plug having an electrode with an end projecting into said chamber, a radio-shielding conduit mechanically and electrically connected to said tubular structure, an ignition conductor in said conduit and extending into said chamber to establish electrical connection with said electrode, there bein spaces in said conduit in communication with said chamber, and a vent fromsaid chamber to the exterior oi said radio-shielding, tubular structure and means for controlling said vent according to operating conditions of said engine.

. 26. The combination with a spark plug for an internal combustion engine, of a tubular, radioshielding casing grounded on said engine through said spark plug, said spark plug having an electrode with an end projecting into said chamber, a radio-shielding conduit mechanically and electrically connected to said tubular structure, an ignition conductor in said conduit and extending into said chamber to establish electricaDconnection with said electrode, there being spaces in said conduit in communication with said cham- 1 her, and a vent from said chamber and clearances to the exterior of said radio-shielding tubular structure and means for controlling said vent.

27. The combination with a spark plug for an internal combustion engine, of a tubular, radioshielding casing grounded on said engine through said spark plug, said radio-shielding structure surrounding a chamber and said spark plug having an electrode with an end projecting into said chamber, a radio-shielding conduit mechanically and electrically connected to said tubular structure, an ignition conductor in said conduit and extending into said chamber to establish electrical connection with said electrode, there being spaces in said conduit in communication with said chamber, and a vent from said chamber and clearances to the exterior of said radio-shielding, tubular structure and thermostatic means for controlling said vent.

28. The combination with a spark plug for an internal combustion engine, of a tubular, radioshielding casing grounded on said engine through said spark plug, said radio-shielding structure surrounding a chamber and said spark plug having an electrode with an end projecting into said chamber, a radio-shielding conduit mechanically an electrically connected to said tubular structure, an ignition conducto in said conduit and extending into said electrode, there being spaces in said conduit in communication with said chamber, and a vent from said chamber and clearances to the exterior of said radio-shielding,

nected to said casing, a second conductor in said;

conduit and extending into said casing, said conductors contacting within a chamber in said cas ing and a vent from said chamber to the exterior of said casing and thermostatic means controlling said vent.

31. A radio-shielding electrical connection comprising in combination, a radio-shielding casing, a conductor entering therein, a conduit connected in said casing, a second conductor insaid conduit and extending into said casing, said conductors contacting within a chamber in said casing, a vent from said chamber to the exterior thereof, and means controlling said vent, there being clearances in said casing and conduit about said conductors and means for supplying fluid under pressure to said clearances.

MELVILLE F. PETERS.

DAVID INGALLS. 

